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Spring配置文件解析之BeanDefinitionParserDelegate詳解

更新時間：2024年02月14日 08:47:16 作者：軍偉@

這篇文章主要介紹了Spring配置文件解析之BeanDefinitionParserDelegate詳解,對于Spring的配置文件的解析處理操作是在BeanDefinitionParserDelegate中進行處理操作,接下來我們簡單介紹一下BeanDefinitionParserDelegate所做的處理操作,需要的朋友可以參考下

Spring的BeanDefinitionParserDelegate

上一篇Spring配置文件解析之BeanDefinitionDocumentReader詳解中我們已經(jīng)了解到對于Spring的配置文件的解析處理操作是在BeanDefinitionParserDelegate中進行處理操作，接下來我們簡單介紹一下BeanDefinitionParserDelegate所做的處理操作。

首先BeanDefinitionParserDelegate中定義了其會解析xml的spring元素標簽，并且還有說明一點的是Spring解析xml的標簽是通過命名空間Namespace來決定的，BeanDefinitionParserDelegate中定義了如下命名空間，只會支持解析這個命名空間中的標簽元素。

public static final String BEANS_NAMESPACE_URI = "http://www.springframework.org/schema/beans";

BeanDefinitionParserDelegate中定義的spring的標簽元素如下：

	public static final String BEANS_NAMESPACE_URI = "http://www.springframework.org/schema/beans";
	public static final String MULTI_VALUE_ATTRIBUTE_DELIMITERS = ",; ";
	public static final String TRUE_VALUE = "true";
	public static final String FALSE_VALUE = "false";
	public static final String DEFAULT_VALUE = "default";
	public static final String DESCRIPTION_ELEMENT = "description";
	public static final String AUTOWIRE_NO_VALUE = "no";
	public static final String AUTOWIRE_BY_NAME_VALUE = "byName";
	public static final String AUTOWIRE_BY_TYPE_VALUE = "byType";
	public static final String AUTOWIRE_CONSTRUCTOR_VALUE = "constructor";
	public static final String AUTOWIRE_AUTODETECT_VALUE = "autodetect";
	public static final String DEPENDENCY_CHECK_ALL_ATTRIBUTE_VALUE = "all";
	public static final String DEPENDENCY_CHECK_SIMPLE_ATTRIBUTE_VALUE = "simple";
	public static final String DEPENDENCY_CHECK_OBJECTS_ATTRIBUTE_VALUE = "objects";
	public static final String NAME_ATTRIBUTE = "name";
	public static final String BEAN_ELEMENT = "bean";
	public static final String META_ELEMENT = "meta";
	public static final String ID_ATTRIBUTE = "id";
	public static final String PARENT_ATTRIBUTE = "parent";
	public static final String CLASS_ATTRIBUTE = "class";
	public static final String ABSTRACT_ATTRIBUTE = "abstract";
	public static final String SCOPE_ATTRIBUTE = "scope";
	private static final String SINGLETON_ATTRIBUTE = "singleton";
	public static final String LAZY_INIT_ATTRIBUTE = "lazy-init";
	public static final String AUTOWIRE_ATTRIBUTE = "autowire";
	public static final String AUTOWIRE_CANDIDATE_ATTRIBUTE = "autowire-candidate";
	public static final String PRIMARY_ATTRIBUTE = "primary";
	public static final String DEPENDENCY_CHECK_ATTRIBUTE = "dependency-check";
	public static final String DEPENDS_ON_ATTRIBUTE = "depends-on";
	public static final String INIT_METHOD_ATTRIBUTE = "init-method";
	public static final String DESTROY_METHOD_ATTRIBUTE = "destroy-method";
	public static final String FACTORY_METHOD_ATTRIBUTE = "factory-method";
	public static final String FACTORY_BEAN_ATTRIBUTE = "factory-bean";
	public static final String CONSTRUCTOR_ARG_ELEMENT = "constructor-arg";
	public static final String INDEX_ATTRIBUTE = "index";
	public static final String TYPE_ATTRIBUTE = "type";
	public static final String VALUE_TYPE_ATTRIBUTE = "value-type";
	public static final String KEY_TYPE_ATTRIBUTE = "key-type";
	public static final String PROPERTY_ELEMENT = "property";
	public static final String REF_ATTRIBUTE = "ref";
	public static final String VALUE_ATTRIBUTE = "value";
	public static final String LOOKUP_METHOD_ELEMENT = "lookup-method";
	public static final String REPLACED_METHOD_ELEMENT = "replaced-method";
	public static final String REPLACER_ATTRIBUTE = "replacer";
	public static final String ARG_TYPE_ELEMENT = "arg-type";
	public static final String ARG_TYPE_MATCH_ATTRIBUTE = "match";
	public static final String REF_ELEMENT = "ref";
	public static final String IDREF_ELEMENT = "idref";
	public static final String BEAN_REF_ATTRIBUTE = "bean";
	public static final String LOCAL_REF_ATTRIBUTE = "local";
	public static final String PARENT_REF_ATTRIBUTE = "parent";
	public static final String VALUE_ELEMENT = "value";
	public static final String NULL_ELEMENT = "null";
	public static final String ARRAY_ELEMENT = "array";
	public static final String LIST_ELEMENT = "list";
	public static final String SET_ELEMENT = "set";
	public static final String MAP_ELEMENT = "map";
	public static final String ENTRY_ELEMENT = "entry";
	public static final String KEY_ELEMENT = "key";
	public static final String KEY_ATTRIBUTE = "key";
	public static final String KEY_REF_ATTRIBUTE = "key-ref";
	public static final String VALUE_REF_ATTRIBUTE = "value-ref";
	public static final String PROPS_ELEMENT = "props";
	public static final String PROP_ELEMENT = "prop";
	public static final String MERGE_ATTRIBUTE = "merge";
	public static final String QUALIFIER_ELEMENT = "qualifier";
	public static final String QUALIFIER_ATTRIBUTE_ELEMENT = "attribute";
	public static final String DEFAULT_LAZY_INIT_ATTRIBUTE = "default-lazy-init";
	public static final String DEFAULT_MERGE_ATTRIBUTE = "default-merge";
	public static final String DEFAULT_AUTOWIRE_ATTRIBUTE = "default-autowire";
	public static final String DEFAULT_DEPENDENCY_CHECK_ATTRIBUTE = "default-dependency-check";
	public static final String DEFAULT_AUTOWIRE_CANDIDATES_ATTRIBUTE = "default-autowire-candidates";
	public static final String DEFAULT_INIT_METHOD_ATTRIBUTE = "default-init-method";
	public static final String DEFAULT_DESTROY_METHOD_ATTRIBUTE = "default-destroy-method";

接下來我們看一下對一個簡單的bean注入的配置的解析處理操作。

<bean id="transaction" name="transaction" class="com.xxxx.aop.two.Transaction"></bean>

這里需要解析的元素有id，name和class三個標簽，在上面均有定義。

在parseBeanDefinitionElement中會完成id和name標簽的解析處理操作，并最終生成BeanDefinitionHolder返回，class標簽的元素解析在parseBeanDefinitionElement中處理

public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {
		//解析id
		String id = ele.getAttribute(ID_ATTRIBUTE);
		//解析name
		String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);
 
		//獲取別名
		List<String> aliases = new ArrayList<String>();
		if (StringUtils.hasLength(nameAttr)) {
			String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, MULTI_VALUE_ATTRIBUTE_DELIMITERS);
			aliases.addAll(Arrays.asList(nameArr));
		}
 
		String beanName = id;
		if (!StringUtils.hasText(beanName) && !aliases.isEmpty()) {
			beanName = aliases.remove(0);
			if (logger.isDebugEnabled()) {
				logger.debug("No XML 'id' specified - using '" + beanName +
						"' as bean name and " + aliases + " as aliases");
			}
		}
 
		if (containingBean == null) {
			checkNameUniqueness(beanName, aliases, ele);
		}
		//解析其他元素標簽
		AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);
		if (beanDefinition != null) {
			if (!StringUtils.hasText(beanName)) {
				try {
					if (containingBean != null) {
						beanName = BeanDefinitionReaderUtils.generateBeanName(
								beanDefinition, this.readerContext.getRegistry(), true);
					}
					else {
						beanName = this.readerContext.generateBeanName(beanDefinition);
						// Register an alias for the plain bean class name, if still possible,
						// if the generator returned the class name plus a suffix.
						// This is expected for Spring 1.2/2.0 backwards compatibility.
						String beanClassName = beanDefinition.getBeanClassName();
						if (beanClassName != null &&
								beanName.startsWith(beanClassName) && beanName.length() > beanClassName.length() &&
								!this.readerContext.getRegistry().isBeanNameInUse(beanClassName)) {
							aliases.add(beanClassName);
						}
					}
					if (logger.isDebugEnabled()) {
						logger.debug("Neither XML 'id' nor 'name' specified - " +
								"using generated bean name [" + beanName + "]");
					}
				}
				catch (Exception ex) {
					error(ex.getMessage(), ele);
					return null;
				}
			}
			String[] aliasesArray = StringUtils.toStringArray(aliases);
			//最終生成BeanDefinitionHolder
			return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);
		}
 
		return null;
	}

接下來我們看看對class標簽的解析處理操作。parseBeanDefinitionElement中會完成對class等其他標簽的解析處理操作，最終生成BeanDefinition返回。

public AbstractBeanDefinition parseBeanDefinitionElement(
			Element ele, String beanName, BeanDefinition containingBean) {
 
		this.parseState.push(new BeanEntry(beanName));
 
		//解析class標簽內(nèi)容
		String className = null;
		if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
			className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
		}
 
		try {
			String parent = null;
			if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
				parent = ele.getAttribute(PARENT_ATTRIBUTE);
			}
			AbstractBeanDefinition bd = createBeanDefinition(className, parent);
 
			parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
			bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));
 
			parseMetaElements(ele, bd);
			parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
			parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
 
			parseConstructorArgElements(ele, bd);
			parsePropertyElements(ele, bd);
			parseQualifierElements(ele, bd);
 
			bd.setResource(this.readerContext.getResource());
			bd.setSource(extractSource(ele));
			//最終生成BeanDefinition返回
			return bd;
		}
		catch (ClassNotFoundException ex) {
			error("Bean class [" + className + "] not found", ele, ex);
		}
		catch (NoClassDefFoundError err) {
			error("Class that bean class [" + className + "] depends on not found", ele, err);
		}
		catch (Throwable ex) {
			error("Unexpected failure during bean definition parsing", ele, ex);
		}
		finally {
			this.parseState.pop();
		}
 
		return null;
	}

總結(jié)

繞了那么一大圈，Spring配置文件的解析處理操作是在BeanDefinitionParserDelegate中完成，當然也是只是完成了對Beans這個命名空間中的元素的解析處理操作，對于其他的命名空間是通過其他解析器進行解析操作的，接下來我們會進行分析，BeanDefinitionParserDelegate做的處理操作就是將bean的各種標簽解析成BeanDefinition對象，并組裝成BeanDefinitionHolder返回。

到此這篇關(guān)于Spring配置文件解析之BeanDefinitionParserDelegate詳解的文章就介紹到這了,更多相關(guān)Spring的BeanDefinitionParserDelegate內(nèi)容請搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家！

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